286 TABLE OP GENERA. 



II. BIVALVES. 



Shell formed of two valves, connected together by a ligament 

 on the dorsal edge. 



* Shell with diverging hinge-teeth ; inside not pearly. 

 CYCLAS. Shell oblong, nearly equilateral. p. 252. 

 PISIDIUM. Shell ovate, inequilateral. p. 264. 



** Shell with irregular hinge-teeth ; inside pearly. 

 UNIO. Shell with distinct posterior lateral laminar teeth. 



p. 278. 

 ALASMODON. Shell without any lateral teeth. p. 276. 



*** Hinge toothless. 



ANODON. Shell ovate, pearly ; umbones (dorsal) blunt. p. 27 1 . 

 DREISSENA. Shell triangular, not pearly ; umbones (anterior) 

 acute. p. 259. 



II. 



AN OUTLINE OF THE HISTORY OF THE VABIOUS ADDITIONS 

 WHICH HAVE BEEN MADE FROM TIME TO TIME TO THIS FART 

 OF OUR FAUNA. 



1st. MERRET, who in 1667 published the first attempt at a 

 British Fauna, in his Pinax, has recorded six species : 



1. Anodon cygneus (Mytilus^ or Horse Muscle). 2. Lim- 

 neus (L. stagnalisf). List. Ang. t. 2. f. 1. 3. Limax maxi- 

 mus. 4. Helix Pomatia, which he says is found in Sussex. 

 5. Helix rufescens (Cochlea alba minor ubigue in hortis). 6. 

 Helix nemoralis (Cochlea vulgar is testa variegata). List. Ang. 

 t. 2. f. 3. 



2nd. Dr. LISTER, in 1678, commenced a separate work on 

 the British shells and, as was to be expected from his accuracy 

 and the extent of his researches, he may be considered as the 

 originator of this part of the science. He described and figured 

 in this work, and in his larger work on conchology (where he 

 marked the British species with an A), the following species, 



